The landmark criminal case involving postpartum psychosis was that of Andrea Yates, who drowned her five children in a bathtub 25 years ago. She said at the time she believed she would be saving them from Satan.
A Houston jury rejected the insanity defense and found her guilty. But then her lawyer, George Parnham, discovered that the state’s expert witness had given false testimony about, of all things, a “Law and Order” episode.
Ms. Yates was granted a new trial, and the second time, the jury found her not guilty by reason of insanity.
In the U.S. legal system, postpartum psychosis cases are treated like any other insanity defense — they must meet that state’s definition of insanity to be successful. States generally use a variation of one of several definitions. The first, and most common, is the strictest: Defendants must prove that they did not understand what they were doing or did not know that it was wrong.
Another definition allows that the defendant may have known that what they were doing was wrong, but could not resist the impulse to do it. A third asks juries to consider whether, but for the defendant’s “mental defect,” the crime would have occurred. A fourth says that the defendant must have been either unable to understand their action or unable to stay within the confines of the law.
Massachusetts, where the Lindsay Clancy trial took place, uses one of the less restrictive definitions. Unusually, it requires the prosecution, not the defense, to prove that a mentally ill defendant “retained the substantial capacity to appreciate the wrongfulness or criminality of their conduct and to conform their conduct to the requirements of the law.”
Whatever the definition, being diagnosed with a severe mental illness is not enough to qualify as insane, said Dr. Allison Horan, a reproductive health and forensic psychiatrist.
“I think there is a little bit of a misconception in the public that if someone has postpartum psychosis, it equals no criminal responsibility. And if they don’t, it means criminal responsibility,” Dr. Horan said. “That’s not actually how the legal system thinks about it.”
Experts say that whether a defendant had postpartum psychosis can be difficult to prove in court.
That’s partly because it’s a complex diagnosis. Symptoms often include paranoia and a break from reality, making it challenging for doctors to rely on patients’ descriptions of what they are experiencing. And for some patients with the disorder, their mental state can vary by the hour.
“It’s a condition typified by alternating between periods of being lucid and periods of being out of your mind,” said Michelle Oberman, a legal scholar who has studied cases of mothers who kill.
In the Clancy case, prosecutors have argued that Ms. Clancy was calculating and methodical on the day she strangled her three children to death, sending her husband to run errands to get him out of the way. But the defense has said that after he left the house, she heard a voice ordering her to kill them and herself.
Cases of maternal infanticide are so rare that it is difficult to determine whether there have been any trends in legal outcomes, Dr. Horan said.
Still, some limited and not-too-recent research suggests that women who kill their children may have a greater chance of being acquitted by reason of insanity than defendants on trial for other crimes. One oft-cited 1991 study found that about 1 percent of defendants pleaded insanity, and of those, about a fourth were successful.
By contrast, a 2012 study of 34 cases in which a woman was charged with killing her baby found that insanity defenses were successful in almost half of them. Last week, a New York judge ruled that a mother who killed her two young children in 2022 was not responsible because of mental disease or defect.
The United States is an outlier in how it treats such cases. Some three dozen other countries have special criminal statutes governing postpartum infanticides that set a significantly lower penalty or refer mothers to treatment instead of incarceration.
There have been attempts to pass such a law in several states, including Texas, California and Massachusetts. But only one has succeeded, in Illinois, which passed a law in 2018 that allows postpartum depression and postpartum psychosis to be considered mitigating factors in the sentencings of women convicted of crimes.
The Illinois law can also be used to reduce the sentences of women who were previously convicted. In 2021, the law contributed to a decision to grant parole to a woman convicted in 1990 of killing her infant daughter who was serving life in prison.
Those who are found not guilty by reason of insanity do not walk free — they are generally committed to a psychiatric hospital indefinitely. Often, they stay there longer than they would have been incarcerated had they pleaded guilty.
Ms. Yates remains in the Kerrville State Hospital in Texas. Each year, she waives the opportunity to be evaluated for release.
